This invention relates to a clutch-brake mechanism for disposition in the drive transmission of powered implements and machinery. The mechanism is interposed between a drive and driven member and provides for simultaneous disengagement of the clutch and braking of the driven member without interruption of the power source.
Reference is made to the clutch-brake mechanism for a lawn mower disclosed in FIGS. 2 and 3 of Wick U.S. Pat. No. 4,044,533. The referenced patent discloses a straight centrifugal clutch design wherein a pair of segmental clutch shoes associated with a driven member are intended to move radially into and out of clutch engagement with a drive member. In the referenced patent, springs are depicted for normally biasing the clutch shoes outwardly to make the intended driving engagement with the drive member. In the straight centrifugal clutch design, radial movement of the clutch shoes outwardly to engage and clutch the drive member would be accomplished solely by springs. With relatively light springs biasing the clutch shoes outwardly in the referenced structure, even with up to 40 lbs. of radial spring force per shoe, inadequate load pickup characteristics will likely be evidenced resulting in substantial slippage of the clutch and generation of such high temperatures in the mechanism that annealing and weakening of the springs and other parts is likely along with creation of a fire hazard in any fire prone environment. If, on the other hand, relatively heavy springs are used to bias the clutch shoes outwardly with reasonable assurance of lock-in, the clutch size to accommodate the heavy springs will likely be impractical for applications such as lawn mowers, and/or a fatiguing manual force on a deadman control or the like would be necessary to actuate the braking springs needed to override the clutch springs, and/or the sudden application of end load inertia likely would immediately stall and kill the power source.
Reference is also made to Weber U.S. Pat. No. 2,675,103 which also discloses a straight centrifugal clutch that relies solely on springs to energize the clutch.
It is generally an object of this invention to provide a centrifugal clutch design which does not rely solely on springs to energize the clutch shoes and therefore relatively light springs may be utilized. With light springs the clutch unit can be reasonably small and therefore compatible for use in lawn mowers, chain saws and other relatively small powered implements.